1. Field of the Invention
The present invention relates to a contact structure, a method of manufacturing such a contact structure, a semiconductor device, and a method of manufacturing such a semiconductor device. More specifically, the present invention relates to a contact structure that can inhibit the elevation the resistance of the contact even at the time of performing heat-treatment, a method of manufacturing such a contact structure, a semiconductor device, and a method of manufacturing such a semiconductor device, a semiconductor device that utilizes such a contact structure, and a method of manufacturing such a contact structure.
2. Background Art
The present invention relates to a contact structure typically used for the connection between the diffused layer in the Si substrate of a semiconductor device and metal wirings formed on the upper surface of the insulating layer on the Si substrate; and a method of manufacturing such a contact structure. The present invention will be described below referring to such a case as an example.
FIGS. 5 and 6 are schematic sectional views for illustrating a conventional contact structure.
A method of forming such a contact structure will be described below referring to FIG. 5.
First, an insulating layer 4 is formed on the surface of a Si substrate 2, for example, by a CVD method. The insulating layer 4 is subjected to exposure to the light, etching, on the like to form a connection hole 6. As FIG. 5A shows, the connection hole 6 passes through the insulating layer 4, and the Si substrate 2 is exposed on the bottom 6A of the connection hole 6.
Next, on the inner wall of the connection hole 6, a TiN/Ti film 14 is formed by a sputtering technique as a barrier layer for preventing diffusion and reaction between the conductive member and the Si substrate 2.
If the Si substrate 2 is maintained at a high temperature during the formation of the TiN/Ti film 14, Ti in the TiN/Ti film 14 reacts with Si in the Si substrate 2 at the bottom 6A of the connection hole 6, where the Ti film laminated earlier contacts the Si substrate 2, to form a silicide as FIG. 5B shows. Even if the Si substrate 2 is not maintained at a high temperature, if the Si substrate 2 is subjected to a heat treatment at a high temperature in a subsequent process, Ti in the TiN/Ti film 14 reacts with Si in the Si substrate 2 to form a silicide. Thus, a TiSi2 film or a TiSi film 32 is formed on the bottom 6A of the connection hole 6.
Next, as FIG. 5C shows, the connection hole 6 filled with W, a conductive member 16, by a CVD method or the like. In other words, W is deposited on the entire surface of the TiN/Ti film 14 until the connection hole 6 is filled.
As described above, a contact structure as FIG. 5C shows is formed.
If the TiSi2 or TiSi film 32 formed on the bottom of the connection hole 6 is subjected to a heat treatment at 700xc2x0 C. or higher during the formation of the TiN/Ti film 14, aggregation occurs, whereby the contact resistance at the TiSi2 or TiSi film 32 elevates. Furthermore, if the aggregation of TiSi2 or TiSi proceeds, voids are formed in this area, and the breakdown of electrical connection may be considered.
In order to solve such problems, as FIG. 6 shows, a method of forming a CoSi2 film, which has the heat resistance higher than the heat resistance of a TiSi2 film, is formed on the bottom of the connection hole 6, may be used instead of the TiSi2 or TiSi film 32.
In this method, first as FIG. 6A shows, a Co film 34 is formed on the upper surface 4A of the insulating film 4, the bottom 6A of the connection hole 6, and the side 6B of the connection hole 6 by sputtering or the like, prior to the formation of the barrier layer 14.
Next, as FIG. 6B shows, heat treatment is performed to allow the Co film 34 to react with the Si substrate, to form a CoSi film 36A on the bottom 6A of the connection hole 6. Then, as FIG. 6C shows, the Co film 34 that has not reacted with the Si substrate is removed, leaving the CoSi film 36A on the bottom 6A of the connection hole 6. Thereafter, the heat treatment is performed again to allow the CoSi film 36A with Si to form a CoSi2 film 36.
Next, as FIG. 6D shows, a TiN/Ti film 14 is formed as a barrier layer. Furthermore, a conductive member 16 is deposited on the surface of the TiN/Ti film 14, and fills the connection hole 6. Thus, a contact structure as shown in FIG. 6E is formed.
However, even if such a CoSi2 film 36 is used, CoSi2 aggregates at a heat-treatment temperature above 750xc2x0 C. As a result, the contact resistance of the CoSi2 film 36 elevates, or voids are formed, and electrical connection may be broken.